Show Assistant provider fallback model switches

docs/release-control/v6/internal/subsystems/ai-runtime.md

@@ -188,7 +188,14 @@ runtime cost control, and shared AI transport surfaces.
    completed the turn, and the drawer must update the in-flight transcript row
    when `provider_fallback` names the next route so message labels, cost
    context, retry decisions, and model-route recovery do not continue to point
-   at the failed provider.
+   at the failed provider. The referenced OpenCode source at fetched
+   `origin/dev` commit `1399323b78a04229d9bfe00c7436d7f41770fda8` renders
+   `ModelSwitchedMessage` as a typed transcript message and appends the
+   effective provider/model route to completed assistant turns in
+   `packages/opencode/src/cli/cmd/tui/feature-plugins/system/session-v2.tsx`.
+   Pulse adapts that by rendering provider fallback route changes as a typed
+   `model_switch` stream row on the active assistant turn instead of hiding the
+   switch in transient status text or assistant prose.
    Interactive Assistant streams must establish the session ID and emit the
    `session` event once as soon as the HTTP SSE writer is ready, before finding
    handoff recovery, model resolution, provider fallback planning,

frontend-modern/src/components/AI/Chat/MessageItem.tsx

@@ -99,6 +99,8 @@ export const MessageItem: Component<MessageItemProps> = (props) => {
         return !!evt.tool;
       case 'pending_tool':
         return !!evt.pendingTool;
+      case 'model_switch':
+        return !!evt.model?.trim();
       case 'approval':
         return !!evt.approval;
       case 'question':
@@ -127,11 +129,12 @@ export const MessageItem: Component<MessageItemProps> = (props) => {
   });
   const visibleMessageContent = () =>
     stripAssistantOutputArtifacts(props.message.content || '').text;
-  const messageModelLabel = () => {
-    const model = props.message.model?.trim();
+  const modelRouteLabel = (route?: string) => {
+    const model = route?.trim();
     if (!model) return '';
     return props.getModelRouteLabel?.(model) || formatAIModelRouteLabel(model);
   };
+  const messageModelLabel = () => modelRouteLabel(props.message.model);
 
   // Check if currently streaming content (no tools pending, still streaming)
   const isStreamingText = () =>
@@ -346,6 +349,22 @@ export const MessageItem: Component<MessageItemProps> = (props) => {
                         />
                       </Match>
 
+                      <Match when={evt.type === 'model_switch' && evt.model?.trim()}>
+                        <div
+                          class="my-2 inline-flex max-w-full items-center gap-2 rounded-md border border-border-subtle bg-surface-alt px-2.5 py-1.5 text-xs text-muted"
+                          role="status"
+                          aria-label="Assistant model route changed"
+                          title={evt.model}
+                        >
+                          <CpuIcon class="h-3.5 w-3.5 shrink-0 text-blue-500" aria-hidden="true" />
+                          <span class="shrink-0">Switched to</span>
+                          {' '}
+                          <span class="truncate font-medium text-base-content">
+                            {modelRouteLabel(evt.model)}
+                          </span>
+                        </div>
+                      </Match>
+
                       {/* Content/text block */}
                       <Match
                         when={

frontend-modern/src/components/AI/Chat/__tests__/MessageItem.test.tsx

@@ -626,6 +626,28 @@ describe('MessageItem', () => {
       expect(screen.queryByText(/Hidden reasoning/i)).not.toBeInTheDocument();
     });
 
+    it('renders provider fallback model switches as typed transcript status', () => {
+      const events: StreamDisplayEvent[] = [
+        { type: 'model_switch', model: 'openrouter:deepseek/deepseek-v4-pro' },
+      ];
+
+      render(() => (
+        <MessageItem
+          message={makeMessage({ role: 'assistant', streamEvents: events })}
+          getModelRouteLabel={(model) =>
+            model === 'openrouter:deepseek/deepseek-v4-pro'
+              ? 'DeepSeek V4 Pro via OpenRouter'
+              : model
+          }
+          {...makeHandlers()}
+        />
+      ));
+
+      expect(
+        screen.getByRole('status', { name: 'Assistant model route changed' }),
+      ).toHaveTextContent('Switched to DeepSeek V4 Pro via OpenRouter');
+    });
+
     it('renders tool execution blocks', () => {
       const events: StreamDisplayEvent[] = [
         {

frontend-modern/src/components/AI/Chat/__tests__/streamEventGrouping.test.ts

@@ -58,6 +58,22 @@ describe('groupStreamEventsForDisplay', () => {
     expect(grouped[2].content).toBe('All healthy.');
   });
 
+  it('keeps content separated across a model-switch boundary', () => {
+    const modelSwitch: StreamDisplayEvent = {
+      type: 'model_switch',
+      model: 'openrouter:deepseek/deepseek-v4-pro',
+    };
+    const grouped = groupStreamEventsForDisplay([
+      content('OpenRouter was unavailable.'),
+      modelSwitch,
+      content('Trying the gateway route now.'),
+    ]);
+
+    expect(grouped.map((e) => e.type)).toEqual(['content', 'model_switch', 'content']);
+    expect(grouped[0].content).toBe('OpenRouter was unavailable.');
+    expect(grouped[2].content).toBe('Trying the gateway route now.');
+  });
+
   it('skips empty deltas', () => {
     const grouped = groupStreamEventsForDisplay([content(''), thinking(''), content('hi')]);
     expect(grouped).toHaveLength(1);

frontend-modern/src/components/AI/Chat/__tests__/useChat.test.ts

@@ -1091,6 +1091,10 @@ describe('useChat', () => {
 
       const assistant = chat.messages().find((m) => m.role === 'assistant')!;
       expect(assistant.model).toBe('gemini:gemini-3.1-flash-lite');
+      expect(assistant.streamEvents).toContainEqual({
+        type: 'model_switch',
+        model: 'gemini:gemini-3.1-flash-lite',
+      });
       expect(assistant.workflowStatus).toEqual(
         expect.objectContaining({
           phase: 'provider_fallback',

frontend-modern/src/components/AI/Chat/hooks/useChat.ts

@@ -692,7 +692,12 @@ export function useChat(options: UseChatOptions = {}) {
 
       if (nextModel) {
         setMessages((prev) =>
-          prev.map((msg) => (msg.id === assistantId ? { ...msg, model: nextModel } : msg)),
+          prev.map((msg) => {
+            if (msg.id !== assistantId) return msg;
+            if ((msg.model || '').trim() === nextModel) return msg;
+            const updated = addStreamEvent(msg, { type: 'model_switch', model: nextModel });
+            return { ...updated, model: nextModel };
+          }),
         );
       }
       if (workflowStatus) {

frontend-modern/src/components/AI/Chat/types.ts

@@ -97,6 +97,7 @@ export type StreamEventType =
   | 'tool'
   | 'content'
   | 'pending_tool'
+  | 'model_switch'
   | 'approval'
   | 'question';
 
@@ -106,6 +107,7 @@ export interface StreamDisplayEvent {
   tool?: ToolExecution;
   pendingTool?: PendingTool;
   content?: string;
+  model?: string;
   toolId?: string; // Used to match pending_tool with completed tool
   approval?: PendingApproval; // For approval_needed events
   question?: PendingQuestion; // For question events